When a polymer surface is exposed to flowing blood, a plasma protein layer is quickly deposited. This is followed by a complex series of events involving platelet activation and aggregation and transport of clotting factors and additional cellular elements to the growing thrombi. We have developed a sensitive in-vivo technique to measure dynamic initial deposition profiles of radiolabeled platelets and proteins on polymeric A-V shunt surfaces. We have used this technique to study in-vivo thrombus deposition to several widely used medical polymers. Each polymer shows a unique protein and platelet response. In addition, when specific plasma proteins were coated onto these polymer surfaces, the thrombus deposition profile was changed over the uncoated surface. We intend to use this technique to explore the mechamism of artificial surface-induced thrombogenesis. Determination of the structural and functional differences observed in adhered cells and platelets onto surfaces found in our model to be either more thrombogenic (i. e., albumin-coated PVC or extruded Biomer) will yield information on the role platelets and cells play in modifying and controlling thrombogenesis on artificial surfaces. The effect of preadsorbing various glycoproteins (including transferrin B- lipoprotein, ceruloplasmin, haptoglobin, plasminogen and C3 complement), "sugar-modified" proteins (i. e , fibronectin, fibrinogen, IgG and a2-macroglobulin which have been desialyated) and "fast" and "slow" forms of a2-macroglobulin onto various surfaces, will increase our knowledge of the relationship between these protein's surface structure and active sites and the mechanism of surface-induced thrombosis. Morphological studies will be conducted on excised shunt sections using SEM, TEM, and HVEM. Monocyte procoagulant and figrinolytic activity will be studied using in-vitro agarose-plasma experiments on excised shunt sections. Platelet Factor 4 and fibrinopeptide A assays will follow platelet activation and fibrin formation in-vivo. A laser light scattering technique will be used to determine the amount and size of emboli released from the surfaces. These studies will provide substantial insight into the mechanism of surface induced thrombogenesis.